The objective of this project is to determine the photobiological mechanisms by which short wavelength light and near ultraviolet radiation cause, or contribute to, retinal photopathology and cataractogenesis after extended exposure to low levels of irradiation using the rhesus monkey eye as a model of human ocular photopathology. A 2500 watt xenon lamp and quartz optical system with associated filters and mirrors provides the radiation source. Retinal photopathology and the repair of retinal lesions will be analyzed by serial fundus photography and light optical and electron microscopy. The effects of anti-inflammatory and photosensitizing agents will be studied. The role of melanin pigmentation will be determined by studying the retinal response in albino vs pigmented rabbits. Also the relative sensitivity to injury of macular and paramacular regions of the retina will be studied. Effects on the lens of daily repeated exposures to one eye, using the other eye as control, will be studied by quantiative measurements of lens transmissivity and fluorescence as a model of cataract. Effects of near ultraviolet radiation on the retina will be studied using aphakic monkeys. If possible an action spectrum for ultraviolet sensitivity of the retina will be determined.